BLOCK DIAGRAM AND PRINCIPLE OF OPERATION OF THE ACS

A block diagram of the margarine preparation line, which shows its composition, including actuators and functionally important structural elements, is shown in Fig. 1.

Rice. 1.

The process begins with the selection of product onto fat scales from deodorized fat tanks along 12 lines and onto water-milk scales along 4 lines. The operator enters recipes for both scales, that is, indicates which line and how much product should be added to the scales. After the set on the scales is completed, the fat and water-milk components are sequentially pumped into the mixer. Pumping is only possible when the receiving tank is empty. Pumping continues until the scales are empty. After this, another batch of components begins to be loaded onto the scales. In the mixers, heating occurs, uniform mixing of the product and pumping it into the working tank. If during pumping the product level in the working tank reaches 95%, the pumping process is suspended. From the working tank, the product is fed using a high-pressure pump through a cooler, where margarine crystallizes, and a decrystallizer to the filling machine.

DRAFTING A FUNCTIONAL DIAGRAM AND DESCRIPTION OF THE MAIN FUNCTIONAL UNITS OF THE ACS

Rice. 2.

Using the block diagrams (Fig. 1, 2), we will draw up a functional diagram of the automated control system.

Rice. 3.

MP - microprocessor; DAC - digital-to-analog converter; K - valve; N - pump; SM - mixer; RB - working tank; DU - level sensor; DD - pressure sensor; DT - temperature sensor; DV - weight sensor; DVL - humidity sensor; KM - switch; ADC - analog-to-digital converter.

Rice. 4.

Used as a TP monitoring device.

CPU:

AMD Athlon 64 X2 6000+ BOX, Windsor core, frequency 3000 MHz, Socket AM2, L2 cache 2048 KB. Average service life - 100,000 hours.

Motherboard:

Gigabyte GA-MA790X-DS4, AMD 790X, PCIe, PCI, 4x DDR2533/667/800, SLI/CrossFire. Average service life - 70080 hours.

Hard drive: Seagate Barracuda ST3500320AS 500 GB, SATA II, 7200 rpm, 16MB. Average service life - 70080 hours.

LCD monitor:

Monitor 18.5" LCD Acer E-Machines E190HQVB, 16:9 HD, 5ms, 5000:1. Average service life - 60,000 hours.

2) Microprocessor SIMATIC S7-300 - CPU 315-2 DP - PROFIBUS

Used as a central processing unit.

Company: Siemens

Rice. 5. Microprocessor SIMATIC S7-300 - CPU 315-2 DP - PROFIBUS

Characteristics:

1. Central processor for executing medium and large programs.

2. High performance.

3. Built-in PROFIBUS DP master/slave interface, servicing distributed I/O systems based on PROFIBUS DP; MPI interface support.

4. Working built-in memory with a capacity of 128 KB, RAM (approximately 43 K instructions); Loadable memory - MMC 8 MB.

5. Flexible expansion options; connection of up to 32 S7-300 modules (4-row configuration).

6. Input voltage: 20.4 - 28.8 V; current consumption: from power supply - 800 mA, power consumption - 2.5 W.

7. CPU/execution time: logical operations - 0.1 μs, word operations - 0.2 μs, fixed-point arithmetic - 2 μs, floating point arithmetic - 3 μs.

8. Built-in communication functions: PG/OP communication functions, global data exchange via MPI, standard S7 communication functions, S7 communication functions (server only)

9. System functions: The CPU supports a wide range of functions for diagnostics, parameter setting, synchronization, alarm, timing measurement, etc.

10. Average service life - 70080 hours.

3) High-speed DAC/ADC with support for SM 321

Used as a signal converter from analog to digital and vice versa.

Company: Siemens

Rice. 6. High speed DAC/ADC

Characteristics:

1. Number of inputs - 32

2. Rated input voltage - DC 24V

3. Channel programmable gain

4. Auto calibration

5. Total current consumption - 35 mA

6. Power consumption - 5.5W

7. Programmable trigger circuit

8. 16-bit counter (10 MHz)

9.Output voltage 10V

10. Average service life - no less than 87600 hours.

4) Temperature sensor with a unified output signal Metran-280-1

Used as a mixture temperature meter.

Company: Metran

Rice. 7. temperature sensor

Characteristics:

1. Convertible temperature range: -50…200 °C

2. 4-20 mA/HART output signal

3. Digital transmission of information via the HART protocol

4. Remote control and diagnostics

5. Galvanic isolation of input from output

6. Increased protection against electromagnetic interference

7. Minimum measurement subrange: 25 °C

8. Electronic filter 50/60 Hz

9. Power: 18 - 42 VDC

10. Power: 1.0W

11. Calibration interval - 1 year

12. Average service life - no less than 43800 hours.

5) Rosemount 5300 Level Sensor

Used as a fill level meter in a mixer.

Company: Metran

Rice. 8. Level sensor

Characteristics:

1. Measured media: liquid and bulk

2. Measuring range: 0.1 to 50m

3. Output Signals: 4F20 mA with digital signal based on HART or Foundation™ Fieldbus protocol

4. Availability of explosion-proof version

5. Operating temperature: up to 150°C (302°F)

6.Standby current consumption: 21mA

7. Process pressure: from 0.1 to 34.5 MPa;

8. Relative humidity environment: up to 100%

9. Degree of protection from external influences: IP 66, IP67 according to GOST 14254

10. Calibration interval - 1 year

11. Average service life - 43800 hours.

6) Rosemount 2088 Pressure Transmitter

Used as a pressure gauge in the working tank.

Company: Metran

automatic functional technological margarine

Rice. 9.

Characteristics:

1. Upper measurement limits from 10.34 to 27579.2 kPa

2. Basic reduced measurement error ±0.075%; ±0.1%

3. Output signals 4D20 mA/HART, 1D5 V/HART, 0.8D3.2 V/HART

4. Reconfiguring measurement ranges 20:1

5. Additionally: LCD indicator, brackets, valve blocks

6. Ambient temperature range from 40 to 85°C; measured medium from 40 to 121°С

7. Sensor response time no more than 300 ms

8. Instability of characteristics ±0.1% of Pmax for 1 year

11. Average service life - 61320 hours.

7) Omron-D8M weight sensor

Used as a product weight meter in a mixer.

Brand: Omron

Rice. 10.

Characteristics:

2. Digital output

3. Operating temperature range -10…+120°С

4. Upper limit of measurement: 60 MPa:

5. Rated force: 200N

6. Total reduced error, no more than: 5%

7. Maximum current consumption, no more than:

8. Bridge circuit input resistance, Ohm - 450±25.0

9. Bridge circuit output resistance, Ohm - 400±4.0

10. Calibration interval - 2 years

11. Average service life - 52560 hours.

8) Humidity sensor Omron-4000-04

Used as a moisture meter in the working tank.

Brand: Omron

Rice. eleven.

Characteristics:

1. Range of measured relative humidity: 0 - 100%

2. Output signal - voltage

3. Response time - 15 s

4. Rated output current - 0.05mA

5. Output voltage range: 0.8 - 3.9V

7. SIP housing 1.27 mm

8. Calibration interval - 2 years

9. Average service life - 43800 hours.

Used as an actuator for dosing components in the system.

Company: KZMEM

Rice. 12.

Characteristics:

1. Case type - pass-through, cast (brass)

2. Working pressure: 0 - 0.1MPa

3. Coupling connection

5. Power consumption - 0.15W

6. Number of operations - not less than 500,000

7. Response time - no more than 1 s

8. Average service life - 26280 hours.

Used as a device for pumping components in the system.

Firm: Grundfos

Rice. 13.

Characteristics:

1. Working volume from 0.12 to 0.34 cm 3 /rev

2. Working pressure up to 70 MPa

3. Rotation speed from 500 to 3600 rpm

Used as a device for mixing components in the system.

Firm: "Embodiment"

Rice. 14.

Characteristics:

1. Weight - no more than 215 kg

2. Working capacity of the tank - 156 l

3. Technical productivity - no more than 950 l/h

4. Installed power - no more than 3 kW

5. Frequency - 50 Hz

6. Average service life - 35040 hours.

12) Stainless steel tank

Used as a device for preparing the product.

Firm: Unical

Rice. 15.

Characteristics:

1. Tank volume - 300 l

2. Maximum operating temperature - 120 C

3. Maximum operating pressure - 10 bar

4. Average service life - 26280 hours.

For a general acquaintance with the system, a block diagram is provided (Fig. 6.2). Structural scheme - this is a diagram that defines the main functional parts of the product, their purpose and relationships.

Structure - it's a collection of parts automated system, into which it can be divided according to a certain criterion, as well as the ways of transmitting the impact between them. In general, any system can be represented by the following structures:

• ? constructive - when each part of the system represents an independent constructive whole;
• ? functional - when each part of the system is designed to perform a specific function (full information about the functional structure indicating the control loops is given in the automation diagram);

Rice. 6.2.

? algorithmic - when each part of the system is designed to perform a specific algorithm for transforming an input quantity, which is part of the operating algorithm.

It should be noted that for simple automation objects, block diagrams may not be provided.

The requirements for these schemes are established by RTM 252.40 “Automated process control systems. Structural diagrams of management and control.” According to this document, constructive block diagrams contain: technological divisions of the automation object; points

control and management, including those not included in the project being developed, but having a connection with the designed system; technical personnel and services ensuring operational management and normal functioning of the technological facility; main functions and technical means ensuring their implementation at each control and management point; relationships between parts of an automation object.

Elements of the structural diagram are depicted in the form of rectangles. Individual functional services and officials may be depicted in a circle. Inside the rectangles the structure of this area is revealed. The functions of the automated process control system are indicated by symbols, the interpretation of which is given in the table above the main inscription along the width of the inscription. The relationship between the elements of the structural diagram is depicted by solid lines, merging and branching - by broken lines. The thickness of the lines is as follows: conventional images - 0.5 mm, communication lines - 1 mm, others - 0.2...0.3 mm. The dimensions of the elements of structural diagrams are not regulated and are chosen at your discretion.

The example (Fig. 6.2) shows a fragment of the implementation of a design scheme for managing and monitoring a water treatment plant. The lower part reveals the technological divisions of the automation facility; in the rectangles of the middle part - the main functions and technical means of local control points for units; in the upper part - the functions and technical means of the station’s centralized control point. Since the diagram occupies several sheets, transitions of communication lines to subsequent sheets are indicated and a break in the rectangle is shown, revealing the structure of the automation object.

On the communication lines between individual elements of the control system, the direction of transmitted information or control actions can be indicated; if necessary, communication lines can be marked with letter designations of the type of communication, for example: K - control, C - alarm, DU - remote control, AR - automatic control, DS - dispatch communication, PGS - industrial telephone (loud-speaking) communication, etc.

1. Hierarchical three-level structure of automated process control systems

Most often, distributed automated process control systems have a three-level structure. An example of a block diagram of a complex of technical means of such a system is shown in Figure 1.

At the top level with the participation of operational personnel, the tasks of process dispatching, optimization of modes, calculation of technical and economic indicators of production, visualization and archiving of the process, diagnostics and correction are solved software systems. The upper level of the automated process control system is implemented on the basis of servers, operator (work) and engineering stations.

On the Middle level- tasks automatic control and regulation, start-up and shutdown of equipment, logic-command control, emergency shutdowns and protections. The middle level is implemented on the basis of a PLC.

Lower (field) level The automated process control system ensures the collection of data on the parameters of the technological process and the condition of the equipment, and implements control actions. The main technical means of the lower level are sensors and actuators, distributed input/output stations, starters, limit switches, and frequency converters.

Fig.1

2. I/O level (field level)

Input signals from sensors and control actions on actuators can be supplied directly to the PLC (come from the PLC). However, if the TOU has a significant territorial extent, this will require long cable lines from each device to the PLC. Such a technical solution may not be rational for two reasons:

• high cost of cable products;
• increase in the level of electromagnetic interference with increasing line length.

In such a situation, it is more rational to use distributed peripheral stations located in close proximity to sensors and actuators. Such stations contain the necessary input and output modules, as well as interface modules for connecting to the PLC via a digital fieldbus (for example, using the Profibus DP, or Modbus RTU protocol). Digital transmission of all signals is carried out over one cable with a high level of noise immunity. So-called smart sensors and actuators (which include controllers and other units that provide signal conversion into digital form and implement data exchange via the field bus) can also be directly connected to the field bus.

A simplified I/O diagram using a distributed peripheral station is shown in Figure 2. The Profibus DP (Process field bus Distributed Periphery) field bus allows you to connect up to 125 devices, up to 32 per segment (PLCs, distributed peripheral stations, smart sensors and actuators). A distributed edge station consists of three main components:

• a base panel (Baseplate), on which I/O modules and interface modules are installed in special slots, or a special profile rail on which the modules are mounted;
• input/output modules (I/O Modules);
• Interface modules that provide data exchange with the PLC via a digital field bus.

Rice. 2

The number of slots for installing modules can be different (most often from 2 to 16). The leftmost slot is usually used to install an interface module. The power supply can be installed on the base panel or a separate (external) unit can be used. There are two buses running inside the base panel: one serves to supply power to the installed modules; the other is for information exchange between modules.

Figure 3 shows a photo of a Eurotherm model 2500 distributed input/output node. The base panel contains 8 input/output modules and a Profibus DP interface module, and the power supply is external. Figure 4 shows a photo of the Siemens ET 200M distributed peripheral station. The base panel contains 6 signal modules (input/output modules), 1 Profibus DP interface module (far left) and a power supply.

Fig.3

Fig.4

2.1 Signal modules (input/output modules)

I/O modules come in 4 types:

1) Analog input signal modules (AI, analogue input). They receive electrical signals of a unified range from sensors connected to its inputs, for example:

• 0-20 or 4-20 mA (current signal);
• 0-10 V or 0-5 V (potential signal);
• Thermocouple (TC) signals are measured in millivolts;
• signals from thermal resistance devices (RTD).

Let's say we have a pressure sensor with a measuring range of 0-6 bar and a current output of 4-20 mA. The sensor measures pressure P, which is currently 3 bar. Since the sensor linearly converts the measured pressure value into a current signal, the output of the sensor will be:

The input of the AI ​​signal module, configured for the same ranges (4-20 mA and 0-6 bar), accepts a 12 mA signal and does the reverse conversion:

Matching the range of the electrical signal between the module input and the output of the sensor connected to it is mandatory for correct operation of the system.

2) Discrete input signal modules (DI, discrete input). They receive a discrete electrical signal from the sensors, which can have only two values: either 0 or 24 V (in rare cases, 0 or 220 V). The DI module input can also respond to a closed/opened contact in the circuit connected to it. Contact-type sensors, manual control buttons, status signals from alarm systems, drives, positioning devices, etc. are usually connected to DI.

Let's say we have a pump. When it is not working, its status (output) contact is open. The corresponding digital input of the DI signal module is in state “0”. As soon as the pump is started, its status contact closes and 24 V voltage goes to the DI input terminals. The module, having received voltage at the discrete input, switches it to state “1”.

3) Discrete output signal modules (DO, discrete output). Depending on the internal logical state of the output (“1” or “0”), it sets the voltage at the terminals of the discrete output to 24 V or 0 V, respectively. There is an option when the module, depending on the logical state of the output, simply closes or opens the internal contact (relay type module). DO modules can control actuators, shut-off valves, light signal lights, turn on sound alarms, etc.

4) Analog output signal modules (AO, analogue output) are used to supply a current control signal to actuators with an analogue control signal. Let's say a control valve with a 4-20 mA control input needs to be opened 50%. In this case, current I out is supplied to the corresponding output AO, to which the valve input is connected:

Under the influence of an input current of 12 mA, the valve moves to 50% opening.

The range of the electrical signal between the output of the module and the input of the actuator connected to it is required. An input/output module is also characterized by its channel capacity – the number of inputs/outputs, and, consequently, the number of signal circuits that can be connected to it. For example, the AI4 module is a four-channel analog input module. You can connect 4 sensors to it. DI16 is a discrete input module with sixteen channels. You can connect 16 status signals from technological units to it.

IN modern systems The arrangement of I/O modules on the base board is not strictly regulated, and they can be installed in any order. However, one or more slots are usually reserved for installation of a communication module. Sometimes it is possible to install two communication modules at once, operating in parallel. This is done to improve the fault tolerance of the I/O system.

One of the stringent requirements for modern I/O subsystems is the ability to hot-swap modules without turning off the power (hot swap function).

Communication modules provide data exchange between PLCs, distributed peripheral stations, smart sensors and actuators. The modules support one of the communication protocols:

• Profibus DP;
• Profibus PA;
• Modbus RTU;
• HART;
• CAN, etc.

Information exchange is usually carried out using a master-slave mechanism. Only the master device on the bus can initiate data exchange. Slave devices passively listen to all data flowing on the bus, and only if they receive a request from the master device do they send a response back. Each device on the bus has its own unique network address, which is necessary for unique identification. I/O nodes are typically slave devices, while controllers are master devices.

Figure 5 shows a digital fieldbus combining one controller (with monitor) and four I/O nodes. Each device connected to the bus has its own unique address. Let, for example, a PLC with address 1 want to read a pressure sensor. The sensor is connected to a distributed peripheral station with network address 5, to the AI ​​module located in slot 6, input channel 12. Then the PLC generates and sends the following request via the bus:

Rice. 5

Each node listens for all requests on the bus. Node 5 recognizes that the request is addressed to it, reads the sensor reading and generates a response in the form of the following message:

The controller, having received a response from the slave device, reads the data field from the sensor and performs the appropriate processing. Let, for example, after processing the data, the PLC generates a control signal to open the valve by 50%. The valve control input is connected to the second channel of the AO module located in slot 3 of node 7. The PLC generates a command with the following content:

Node 7, listening to the bus, encounters a command addressed to it. It writes the 50% setting to the register corresponding to slot 3, channel 2. At the same time, the AO module generates the required electrical signal at output 2. After which node 7 sends the controller confirmation of the successful execution of the command.

The controller receives a response from node 7 and considers that the command has been completed. This is just a simplified diagram of how the controller interacts with I/O nodes. In real automated process control systems, along with those discussed above, many diagnostic, control and service messages are used. Although the “request-response” (“command-confirmation”) principle itself, implemented in most field protocols, remains unchanged.

Let us recall once again that, along with the input/output circuit discussed above, the automated process control system can use input/output circuits through signal modules installed directly in the slots (or on the profile rail) of the PLC (without using distributed peripheral stations).

2.2 Processing of analog signals during input to the controller

To input an analog signal into the controller and its subsequent processing, it must be digitized, i.e. converted to digital code. The process of signal processing from an analog sensor to use in a controller is shown schematically in Figure 6.

Fig.6 Analog signal processing circuit when input to the controller

Signals from sensors are brought to a standardized level (4 – 20 mA, 0 – 10 V) by normalizing converters (NC) and go through an analog filtering stage. Analog filters eliminate high-frequency noise that can be caused, for example, by electromagnetic interference during signal transmission through a cable.

It should be noted that the signal must be filtered from high-frequency noise before digital processing in the controller. This is a necessary condition correct selection of the sampling period when inputting a signal. The fact is that for adequate restoration of the original analog signal from discrete data, the sampling frequency must be at least twice the highest frequency in the spectral decomposition of the input signal (the spectral composition can be obtained as a result of decomposing the signal into a Fourier series). At a lower sampling frequency, a false component (the so-called pseudo-frequency) will appear in the reconstructed signal, which cannot be detected and eliminated at the digital processing stage. The presence of high-frequency noise will require a very high sampling rate (sensor sampling rate), which will unnecessarily load the controller.

The filtered signals from the sensors are fed to an analog multiplexer, the main purpose of which is to sequentially connect signals from N sensors to a sample-storage device (SSD) and an analog-to-digital converter (ADC) for further processing. This scheme allows you to significantly reduce the total cost of the input system due to the use of only one UVH and ADC for all analog input channels. The UVH remembers the instantaneous value of the signal at the moment the sensor is connected and keeps it constant at its output during the conversion to the ADC.

In the controller, the entered digital signal is checked for physical plausibility and, if necessary, goes through a digital (software) filtering stage.

Is the control circuit in data collection mode. In this case, it is connected to the technological process in a manner selected by the process engineer.

The connection is made through pairing with an object (USO). The measured values ​​are converted into digital form. These quantities are converted into units using the appropriate formulas. For example, to calculate the temperature measured using a thermocouple, the formula T = A * U2 + B * U + C can be used, where U is the voltage at the output of the thermocouple; A, B and C are coefficients. The calculation results are recorded by output devices for subsequent study of the technological process under various conditions. Based on this, it is possible to build or refine a mathematical model of the controlled process.

This mode does not have a direct impact on the technological process. Here I found a cautious approach to the implementation of control methods in automated process control systems. However, this scheme is used as one of the mandatory control subcircuits in other more complex process control schemes.

In this scheme, the process control system operates at the pace of the technological process. The control loop is open, i.e. the outputs of the process control system are not connected to the bodies that control the technological processes. Control actions are carried out operator-technologist receiving recommendations from a computer.

All necessary control actions are calculated by the computer in accordance with the technological process model, the calculation results are provided to the operator in printed form(or in the form of messages on the display). The operator controls the process by changing settings.

Regulators are means of maintaining optimal process control. The operator plays the role of monitor and manager, whose efforts the automated process control system continuously and accurately directs to optimize the execution of the technological process.
The main disadvantage of this control scheme is the presence of a person in the control chain. With a large number of input and output variables, such a control scheme cannot be used due to the limited psychophysical capabilities of a person. However, this type of control also has advantages. It satisfies a cautious approach to new management methods.

Advisor mode provides good opportunities for testing new process models. The process control system can monitor the occurrence of emergency situations, so that the operator can pay more attention to working with the installations, and the process control system can monitor a greater number of emergency situations than the operator.

Supervisory management.

In this scheme, the process control system is used in a closed loop, i.e., the settings of the controllers are specified directly by the system.

1. Management of automated transport and warehouse. In such a system, the computer issues the addresses of the rack cells, and the local automation system of the stacker cranes processes their movement in accordance with these addresses.
2. Melting furnace management. The computer generates setpoint values ​​to control the operating modes of electric furnaces, and local automation, based on computer commands, controls the transformer switches.
3. Machine tools with numerical control.

Direct digital control.

In mode direct digital control(NTS) signals used to actuate the control elements come from the process control system, and the regulators are completely excluded from the control system. Regulators are analog computers that solve a single equation in real time, for example this type:

where y may indicate the position of the valve; k0, k1, k2, k3 – setting parameters, thanks to which the regulator can be configured to operate in various modes; X – the difference between the measured value and the setpoint. If X is not =0, then moving the control body is required to bring the process to the specified mode.

If the regulator uses the first two terms of the equation for its operation, then it is called. If the first three terms are used, then the regulator is proportional-integral, and if are all terms of the equation, then the regulator is proportional-integral-derivative.

The NCU concept allows you to replace regulators with a preset setpoint. Real impacts are calculated, which are transmitted directly to the control bodies in the form of appropriate signals. The NCU diagram is shown in the figure:

Designations introduced:
OO - managed object
D – sensor.

The settings are entered into the ACS by the operator or the computer that performs calculations to optimize the process. The operator must be able to change the settings, control some selected variables, change the ranges of permissible changes in the measured variables, change the settings, and must also have access to the control program. One of the main advantages of the NCU mode is the ability to change control algorithms by making changes to the control program. The main disadvantage of the direct digital control scheme is the possibility of the system in case of computer failure.

IN general view The block diagram of a single-circuit automatic control system is presented in Figure 1.1. An automatic control system consists of an automation object and a control system for this object. Thanks to a certain interaction between the automation object and the control circuit, the automation system as a whole provides the required result of the operation of the object, characterizing its output parameters and characteristics.

Every technological process is characterized by certain physical quantities (parameters). For the rational progress of the technological process, some of its parameters must be maintained constant, and some must be changed according to a certain law. When operating an object controlled by an automation system, the main task is to maintain rational conditions for the technological process.

Let's consider the basic principles of constructing the structures of local automatic control systems. With automatic control, as a rule, three types of problems are solved.

The first type of task includes maintaining one or more technological parameters at a given level. Automatic control systems, problem solving This type is called stabilization systems. Examples of stabilization systems include systems for regulating temperature and humidity in air conditioning units, pressure and temperature of superheated steam in boiler units, speed in steam and gas turbines, electric motors, etc..

The second type of task involves maintaining correspondence between two dependent or one dependent and other independent quantities. Systems that regulate ratios are called automatic tracking systems, for example, automatic systems for regulating the “fuel - air” ratio in the process of fuel combustion or the ratio “steam flow - water flow” when feeding boilers with water, etc.

The third type of problem involves changing a controlled quantity over time according to a certain law. Systems that solve this type of problem are called program control systems. A typical example of this type of system is a temperature control system at heat treatment metal

IN last years Extreme (search) automatic systems are widely used, providing the maximum positive effect of the functioning of a technological object with minimal costs of raw materials, energy, etc.

A set of technical means with the help of which one or more regulated quantities, without the participation of a human operator, are brought into conformity with their constant or specified values ​​varying according to a certain law by generating an impact on the regulated quantities as a result of comparing their actual values ​​with the given ones, is called an automatic control system ( ACP) or automatic control system. From the definition it follows that, in general, the simplest ASR should include the following elements:

control object (OU), characterized by a controlled variable x n. x(t);

a measuring device (MD) that measures the controlled variable and converts it into a form convenient for further conversion or for remote transmission;

a master device (SD), in which a setpoint signal is installed that determines the set value or the law of change of the controlled variable;

a comparison device (CD), in which the actual value of the controlled variable x is compared with the prescribed value g(t) and,

deviation is detected (g(t)- x(t));

a control device (RU), which generates, upon receipt of a deviation (ε) at its input, a regulatory action that must be applied to the controlled object in order to eliminate the existing deviation of the controlled quantity x from the prescribed value g(t);

actuator mechanism (AM). At the output of the reactor plant, the regulating effect has a small power and is issued in a form that is generally not suitable for direct influence on the object of regulation. It is necessary to either strengthen the regulatory impact or transform it into a convenient form x p. For this purpose, special actuators are used, which are the actuator output devices of the regulating element;

regulatory authority (RO). Actuators cannot directly influence the controlled variable. Therefore, the objects of regulation are equipped with special regulatory bodies RO, through which the IM influences the regulated variable;

communication lines through which signals are transmitted from element to element in an automatic system.

As an example, let's consider a larger block diagram of automatic control (Figure 1.1). In the diagram, the output parameters - the result of the operation of the controlled object, are designated x 1, x 2, ……… x n. In addition to these main parameters, the operation of automation objects is characterized by a number of auxiliary parameters (y 1, y 2,.......y n), which must be monitored and regulated, for example, maintained constant.

Figure 1.1. Block diagram of automatic control

During operation, the control object receives disturbing influences f1.... fn, causing deviations of parameters x1.......xn from their rational values. Information about the current values ​​x tek and y tek enters the control system and is compared with their prescribed values ​​(setpoints) g1......gn, as a result of which the control system exerts control actions E1.....En on the object, aimed at compensating for deviations of the current output parameters from the given values.

According to the structure of automatic control systems for an automation object, in particular cases they can be single-level centralized, single-level decentralized and multi-level. At the same time, single-level control systems are systems in which the object is controlled from one control point or from several independent ones. Single-level systems in which control is carried out from one control point are called centralized. Single-level systems, in which individual parts of a complex object are controlled from independent control points, are called decentralized.

2.2 Functionally – technological schemes automatic control

Functional-technological diagram is the main technical document that defines the functional block structure of the devices of the units and elements of the automatic control system, regulation of the technological process (operations) and control of its parameters, as well as equipping the control object with devices and automation equipment. Schemes are also often called simply automation schemes. The composition and rules of implementation are dictated by the requirements of the standards (see Chapter 1).

The functional and technological automation diagram is carried out in one drawing, on which the symbols depict technological equipment, transport lines and pipelines, instrumentation and automation equipment, indicating the connections between them. Auxiliary devices (power supplies, relays, circuit breakers, switches, fuses, etc.) are not shown on the diagrams.

Functional automation diagrams are related to production technology and technological equipment, therefore the diagram shows the placement technological equipment simplified, not to scale, but taking into account the actual configuration.

In addition to technological equipment, functional automation diagrams in accordance with standards depict transport lines for various purposes in a simplified (two-line) and conventional (single-line) manner.

Both construction and study of circuits technical documentation must be carried out in a certain sequence.

Process parameters that are subject to automatic control and regulation;

Functional management structure;

Control loops;

Availability of protection and alarm and accepted mechanism locking;

Organization of control and management points;

Technical means automation, with the help of which the functions of control, alarm, automatic regulation and control are solved.

To do this, you need to know the principles of constructing automatic control systems for process control and conventional images of process equipment, pipelines, instruments and automation equipment, functional connections between individual devices and automation equipment, and have an idea of ​​the nature of the technological process and the interaction of individual installations and units of process equipment.

In a functional diagram, communication lines and pipelines are often shown in a single-line diagram. The designation of the transported medium can be either digital or alphanumeric. (For example: 1.1 or B1). The first number or letter indicates the type of transported medium, and the subsequent number indicates its purpose. Numerical or alphanumeric designations are presented on the shelves of leader lines or above the transport line (pipeline), and, if necessary, in breaks in the transport lines (in this case, the accepted designations are explained in drawings or in text documents (see table 1.1.). On technological objects show those control and shut-off valves, technological devices that are directly involved in monitoring and controlling the process, as well as sampling (sensors), shut-off and regulatory bodies necessary to determine the relative location of sampling points (locations for installing sensors), as well as measurement or control parameters (see table 1.2).

Complete devices (centralized control machines, control machines, semi-sets of telemechanics, etc.) are designated by a rectangle of arbitrary sizes with the type of device indicated inside the rectangle (according to the manufacturer’s documentation).

In some cases, some elements of technological equipment are also depicted on diagrams in the form of rectangles, indicating the names of these elements. At the same time, next to sensors, selective, receiving and other devices similar in purpose, indicate the name of the technological equipment to which they belong.

Table 1.1. Designation of transport pipeline lines according to GOST 14.202 – 69

Table 1.2. Symbols of technological fittings

Name	Designation according to GOST 14.202 - 69
Gate valve through passage (gate)
Electrically operated valve
Three way valve
safety valve
Rotary valve (valve, gate)
Actuator diaphragm
Table 1.3. Output electrical switching elements
Name	Designation according to GOST 2.755 - 87
Contact for switching high current circuit (contactor contact)
Normal contact
Normal contact

To make diagrams easier to read, arrows are placed on pipelines and other transport lines indicating the direction of movement of the substance.

In the functional-technological diagram, as well as in the image of the pipeline through which the substance leaves this system, a corresponding inscription is made, for example: “From the absorption workshop”, “From the pumps”, “To the polymerization circuit”.

Figure 1.2. Image of sensors and sampling devices (fragment)

Conventional graphic symbols of automation equipment are given in tables 1.2., 1.3., 1.4.. Conventional graphic symbols of electrical equipment used in functional automation diagrams should be depicted in accordance with the standards (Table 1.3.). If there are no standard symbols for any automatic devices, you should adopt your own symbols and explain them with an inscription on the diagram. The thickness of the lines of these designations should be 0.5 - 0.6 mm, except for the horizontal dividing line in the symbolic image of the device installed on the switchboard, the thickness of which is 0.2 - 0.3 mm.

The sampling device for all permanently connected devices does not have a special designation, but is a thin solid line connecting the process pipeline or apparatus with the device (Fig. 1.2. devices 2 and 3a). If it is necessary to indicate the exact location of the sampling device or measurement point (inside the graphic designation of the technological apparatus), a circle with a diameter of 2 mm is depicted in bold at the end (Fig. 1.2 devices 1 and 4a).

Table 2.4. Conventional graphic symbols of automation equipment and devices

Name	Symbol according to GOST 21.404 - 85
Primary measuring transducer (sensor) or device installed locally (on a production line, apparatus, wall, floor, column, metal structure). Basic Acceptable
Device installed on a panel, console Basic Permissible
Sampling device without permanent connection of the device
Actuating mechanism
Track switch
Electric bell, siren, horn
Electric heater: a) resistance, c) induction
Recording device
Incandescent lamp, gas discharge (signal)
Three-phase electric machine (M – motor, G – generator)
DC electric machine (motor M, generator G)

To obtain a complete (freely readable) designation of a device or other automation device, a letter symbol is entered into its conventional graphic image in the form of a circle or oval, which determines the purpose, functions performed, characteristics and operating parameters. In this case, the location of the letter determines its meaning. Thus, the letters given in Table 1.5 are the main parameters and functions, and the letters given in Table 1.6 specify the function or parameter.

Table 1.5. Designation of the main measured parameters in automation schemes

To designate manual control, the letter H is used. To designate quantities not provided for by the standard, reserve letters can be used: A, B, C, I, N, O, Y, Z (the letter X is not recommended). The reserved letters used must be deciphered by the inscription on the free field of the diagram.

Below are the designations for clarifying values ​​of the measured quantities.

Table 1.6. Additional letter designations

The letter used to clarify the measured value is placed after the letter indicating the measured value, for example P, D - pressure difference.

The functions performed by devices for displaying information are indicated in Latin letters (see Table 2.7).

Table 1.7. Letter designation of function

Additionally, designations with the letters E, G, V can be used.

All of the above letter designations are placed in the upper part of the circle indicating the device (device).

If several letters are used to designate one device, then the order of their arrangement after the first one, indicating the measured value, should be, for example: TIR - a device for measuring and recording temperature, PR - a device for recording pressure.

When designating devices made in the form of separate blocks and intended for manual operations, the letter H is placed first.

For example in Fig. 1.2 shows an automation diagram using recording instruments for temperature and pressure difference, where to form a symbol for the device (set), the functional purpose is indicated in the upper part of the circle, and its position designation is placed in the lower part of the circle (alphabetic - digital or digital - 1, 2, 4a, 4b, 3a, 3b). Thus, all elements of one set, i.e. one functional group of devices (primary, intermediate and transmitting measuring transducers, measuring device, regulating device, actuator, regulating body) are designated by the same number. In this case, the number 1 is assigned to the first (from the left) set, the number 2 to the second, etc.

To distinguish the elements of one set, a letter index is placed next to the number (the letters Z and O, the outline of which is similar to the outline of numbers, are not recommended): for the primary transducer (sensitive element) - index “a”, for the transmitting transducer - “b” , at the measuring device - “in”, etc. Thus, for one set the full designation of the primary measuring transducer will be 1a, transmitting measuring transducer 1b, measuring (secondary) device 1c, etc. the height of the number is 3.5 mm, the height of the letter is 2.5 mm.